It is often desirable and frequently necessary to sample or test a portion of tissue from humans and other animals, particularly in the diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions and other diseases or disorders. Typically, in the case of cancer, when the physician establishes by means of procedures such as palpation, x-ray or ultrasound imaging that suspicious circumstances exist, a biopsy is performed to determine whether the cells are cancerous. Biopsy may be done by an open or percutaneous technique. Open biopsy removes the entire mass (excisional biopsy) or a part of the mass (incisional biopsy). Percutaneous biopsy, on the other hand, is usually done with a needle-like instrument and may be either a fine needle aspiration (FNA) or a core biopsy. In FNA biopsy, individual cells or clusters of cells are obtained for cytologic examination and may be prepared such as in a Papanicolaou smear. In core biopsy, as the term suggests, a core or fragment of tissue is obtained for histologic examination which may be done via a frozen section or paraffin section. The type of biopsy utilized depends in large part on circumstances present with respect to the patient and no single procedure is ideal for all cases. However, core biopsy is extremely useful in a number of conditions and continues to be used frequently by the medical profession.
To arrive at a definitive tissue diagnosis, intact tissue is needed from an organ or lesion within the body. In most instances, only part of the organ or lesion need be sampled. However, the portions of tissue obtained must be representative of the organ or lesion as a whole. In the past, to obtain tissue from organs or lesions within the body, surgery had to be performed to locate, identify and remove the tissue. With the advent of medical imaging equipment (x-rays and fluoroscopy, computed tomography, ultrasound, nuclear medicine, and magnetic resonance imaging) it has become possible to identify small abnormalities even deep within the body. However, definitive tissue characterization still requires obtaining adequate tissue samples to characterize the histology of the organ or lesion. For example, mammography can identify non-palpable (not perceptible by touch) breast abnormalities earlier than they can be diagnosed by physical examination. Most non-palpable breast abnormalities are benign; some of them are malignant. When breast cancer is diagnosed before it becomes palpable, breast cancer mortality can be reduced. However, it is often difficult to determine if pre-palpable breast abnormalities are malignant, as some benign lesions have mammographic features which mimic malignant lesions and some malignant lesions have mammographic features which mimic benign lesions. Thus, mammography has its limitations. To reach a definitive diagnosis, tissue from within the breast must be removed and examined under a microscope. Prior to the late 1980's, reaching a definitive tissue diagnosis for non-palpable breast disease required a mammographically guided localization, either with a wire device, visible dye, or carbon particles, followed by an open, surgical biopsy utilizing one of these guidance methods to lead the surgeon to the non-palpable lesion within the breast.
Open surgical breast biopsies have many drawbacks. They can be disfiguring, expensive (in terms of direct costs to the patient and indirect costs to society from the patient being away from work), and are imperfect (the error rate for surgical biopsy has been reported to be from 2% to 22%). For example, a localization wire can be incorrectly placed by the radiologist. Even if properly placed, the efficacy of the biopsy may be marred by poor tissue selection by the surgeon, in which the lesion is not harvested. A properly harvested lesion may still suffer from the result of having the wrong section prepared for analysis.
Any of these errors will lead to an incorrect diagnosis of the lesion. Open surgical biopsies also carry a small mortality risk (due to the risks of anesthesia) and a moderate morbidity rate (including bleeding, infection, and fracture or migration of the localizing wire). In cases where multiple lesions are present in the breast, a surgeon is reluctant to biopsy each lesion due to the large tissue mass that must be extracted with each lesion. The most convenient lesion is taken which most often results in an incomplete diagnosis. Finally, all of this must be considered in the context of the frequency of procedures such as breast biopsies. In the United States, alone, it is estimated that open, surgical breast biopsies are performed on over 500,000 women annually. A less invasive alternative has long been sought.
A well known instrument used quite extensively for core biopsies in the past is manufactured by Travenol Laboratories of Deerfield, Ill., and is sold under the mark "TRU-CUT." This manual biopsy instrument at one time enjoyed as much as 98% of the market for such devices. As disclosed in U.S. Pat. No. 3,477,423, the instrument comprises a two-piece assembly: an outer cutting cannula mounted to one hub member and an inner stylet with a sampling notch ground into it mounted to a second hub, with the hubs being slidably interlocked. The instrument is assembled and placed into the body with the outer cutting cannula just to the rear of a lancet point or beveled distal end of the stylet. Upon inserting the device up to or in front of the area to be biopsied, advancement of the assembly is halted. The stylet is manually advanced distally of the cannula with the cannula held stationery. Upon advancement of the stylet, the specimen notch is exposed. Tissue surrounding the stylet prolapses into the specimen notch and the cutting cannula is then manually advanced distally over the stylet, slowly shearing off the tissue entrapped in the stylet's specimen notch. The instrument is then either (a) withdrawn and the stylet advanced distally to expose the tissue for preparation for study or (b) left in place and only the stylet is proximally removed from within the cannula so a determination of successful sampling may be made. If the sampling was not successful, the stylet may be reinserted into the cannula, which remains positioned within the patient, and an attempt to reposition the assembly of stylet and cannula and repeat sampling can be made.
Such a technique using this basic design of a biopsy instrument is referred to as a manual technique. One drawback to the manual technique is that it requires a great deal of manual dexterity and motor coordination, along with the use of both hands, to advance the stylet while maintaining the position of the cannula and then to maintain the position of the stylet while advancing the cannula. Another drawback is that the cannula is advanced relatively slowly, resulting in an extremely poor cutting action and allowing the surrounding tissue an opportunity to collapse, thus making no use of the stored kinetic energy in the material being severed. Further disadvantages are encountered when the tissue volume to be sampled contains areas of higher density than that of surrounding tissue, such as areas of calcification commonly associated with certain types of cancerous growths. A manually inserted sampling device is often incapable of penetrating the denser area of tissue which merely deflects the course of the cannula/stylet structure around the dense area and into the more compliant surrounding tissue.
In the late 1980's, two different stereotactic guidance systems were modified to allow the guiding portion of each system to accommodate spring powered devices such as the Biopty.RTM. (Bard Radiology) gun. As used herein, the term "gun" to refer to tissue sampling devices for "one-handed" operation refers to a design common to many of these devices wherein the shape of the device is adapted to fit the hand of a medical practitioner with a pistol-like grip, complete with a triggering mechanism. Free-hand ultrasound guidance techniques were also developed to guide the Biopty.RTM. gun to breast lesions detected by ultrasound. Although sold to perform a biopsy of the prostate, the "BIOPTY" gun and related "BIOPTY-CUT" needle have also been proposed for performing CT-guided abdominal biopsies. See Parker et al., "Technical Note: Adaptation of the Bard Prostate Biopsy Gun for CT-Guided Abdominal Biopsies," CardioVascular and Interventional Radiology, 12: 50-52 (1989); and Parker et al., "Image-directed Percutaneous Biopsies with a Biopsy Gun," Radiology, 171: 663-669 (1989). The BIOPTY-CUT 18-gauge needle is not adapted to be used apart from the BIOPTY gun, but needle placement is more cumbersome when the gun is attached. As contemplated by Parker et al., use of such devices can be adapted to a "three-hand" technique in which the medical practitioner's left hand manipulates a transducer for an imaging system; simultaneously, the practitioner's right hand grasps and guides the sampling device, typically at the base of the stylet/cannula assembly and forward of the handle portion of the device. When the practitioner is satisfied that the sampling device is properly positioned, he gives a "go" signal and the "third hand," belonging to a nurse or technician, triggers the sampling device in response to the practitioner's command.
Parker et al. describe a technique of placing the BIOPTY-CUT needle within the body before attachment of the needle to the gun. A short section of sterile plastic sheath is inserted around the cutting needle between the hub of the cannula and the hub of the cutting needle to maintain the two in fixed relationship; following placement of the BIOPTY-CUT needle, the needle is "pinned" to the skin before the gun is attached to avoid displacement of the needle tip longitudinally or introduction of unwanted angulation. The short section of plastic sheath is removed, and the needle hub assembly is then inserted into the spring-loaded sleds of the BIOPTY biopsy gun.
With image-guided percutaneous core breast biopsy, it should be possible to greatly reduce the number of open, surgical breast biopsies performed. However, there are limiting factors with image-guided breast biopsies. Manually operated two-step devices are awkward to manipulate, and the tissue samples obtained may often be unsatisfactory. The depths to which the stylet and the cannula are driven into the tissue mass must be carefully controlled for accuracy and efficiency. Caution is required, as well, in applying the force with which the stylet and cannula are plunged forward. Too little force may not sever the tissue sample from the mass; too much force may cause unnecessary damage to the surrounding vital tissues.
A variety of biopsy needles and guns have been described and used for obtaining tissue specimens. One such biopsy gun currently used is described in U.S. Pat. No. Re. 34,056, entitled "TISSUE SAMPLING DEVICE," issued to Lindgren et al. Additional examples of biopsy gun devices are disclosed in U.S. Pat. Nos. 4,600,014 and 4,958,625. The Lindgren Automatic Core Biopsy Device (ACBD) is an instrument which propels a needle set with considerable force and speed in order to pierce a tumor mass and collect the tissue sample. The ACBD has allowed physicians to accurately test tissue masses in the early stages of growth and has contributed to the medical trend of early diagnosis and successful treatment of cancer. The ACBD allows a biopsy to be performed on tumor masses as small as two millimeters in diameter. This procedure is performed under ultrasound or X-ray guidance. Tumors of this size cannot be biopsied reliably by hand since the tumor is about the same size as the biopsy needle. Manual attempts at biopsy often push the tumor away without piercing the mass. Automatic puncture devices are capable of accelerating the biopsy needle at such a velocity that even a small tumor can be pierced.
Such devices use a design comprising a handle held in a physician's palm, and a guide tube extending forwardly of the handle. A cannula is slidably disposed within the guide tube and is movable from within the guide tube forwardly out of the distal end of the guide tube. A sampling stylet is telescopically disposed within the cannula and projects from the rear of the handle. In an automatic mode of operation, the cannula, when in the retracted position, is spring loaded by means of a compressed spring. A release lever, which works against the compressed spring, is activated to release compression of the spring which then expands and pushes the cannula outwardly over the stylet. This instrument, as stated, requires two handed operation. Also, since the stylet is not removable proximally from within the handle, the entire instrument must be withdrawn to obtain access to the sample.
A fully automatic instrument manufactured by Radiplast, Inc. of Sweden is described in U.S. Pat. No. 4,699,154. This instrument comprises a reusable, spring-loaded box-shaped housing or handpiece, which activates a disposable cannula and stylet set. Both the stylet and cannula are activated in rapid succession. The instrument has the advantage of reducing the dexterity and motor coordination necessary in the use of manual devices and also eliminates the slow cutting action of the manually advanced cannula, replacing it with a very quick, clean cut. This instrument, however, also has its drawbacks. First, the reusable handpiece is very large, heavy, cumbersome, and expensive. They are also typically spring-powered devices and must be manually cocked with some sort of plunger bar. Such "cocking" of the gun requires considerable force and the gun must be cocked for each biopsy cut. When actuated, the springs provided in the gun accelerate the needles until a mechanical stop position is reached which can create a loud snapping noise and jerking motion which is a problem both to the physician and the patient. Its weight and the awkwardness in use preclude it from being used with imaging equipment other than ultrasound, inasmuch as it must be inserted into the body with the user maintaining control of the handpiece at all times. Thus, the patient cannot be imaged with many conventional radiographic apparatus, such as CAT scanners. A further drawback is encountered in automatically activating both the stylet and the cannula, as opposed to activating the stylet manually, in that the rapid speed at which the cannula follows the stylet into the tissue does not allow much tissue to collapse into the specimen notch, limiting the size of the sample.
Various attempts to overcome one or more of the disadvantages of the ACBD have been made. U.S. Pat. No. 5,183,052, entitled "AUTOMATIC BIOPSY INSTRUMENT WITH CUTTING CANNULA," issued to Terwilliger describes a biopsy instrument having a stylet and a cannula wherein the instrument urges the cannula past the stylet in order to collect a tissue sample and simultaneously causes a vacuum to be communicated to the cannula in order to assist the collection of the tissue sample by the cannula.
U.S. Pat. No. 5,183,054, entitled "ACTUATED BIOPSY CUTTING NEEDLE WITH REMOVABLE STYLET," issued to Burkholder et al., discloses a biopsy device having a tubular cannula through which a stylet, having a stylet cavity near the distal end, is placed. The stylet is removable from the cannula and removed from the biopsy device through the housing so that the tissue sample obtained by the biopsy device may be manually retrieved while the cannula remains in place within the patient, near the area being sampled. Thereafter, the stylet may be reinserted through the housing and cannula into the patient's tissue where additional tissue samples may be obtained. In this way, trauma to the tissue that ordinarily occurs upon reinsertion of the cannula and stylet is minimized.
U.S. Pat. No. 5,234,000, entitled "AUTOMATIC BIOPSY DEVICE HOUSING A PLURALITY OF STYLETS," issued to Hakky et al. describes a biopsy device for taking a plurality of samples of tissue from a living being. The device comprises a housing having a portion arranged to be held by a person using the device, a cannula having a proximal portion and a distal portion and being coupled to the housing. A plurality of stylets are located in the housing, with each of the stylets having a proximal end, a distal end, and a tissue receiving notch located adjacent the distal end. Each stylet is individually propelled through the cannula into the body so that a portion of the tissue prolapses into the notch. The Burkholder et al. and Hakky et al. devices share all of the disadvantages of needle-type devices with the exception that they are not limited to acquiring a single sample. In addition, transportation of samples by withdrawing stylettes from the instrument may compromise quality of the specimens through prolonged contact with the inside surface of the cannula.
U.S. Pat. No. 5,195,533, entitled "BIOPSY NEEDLE INSTRUMENT FOR STORING MULTIPLE SPECIMENS," issued to Chin et al. describes a biopsy needle instrument which includes a housing, an axially elongated stylet extending from the housing and a cannula coaxially extending from the housing and disposed about the stylet means. The stylet and cannula can move relative to each other and to the housing between extended and retracted positions. The stylet and cannula define, during a given operation, a specimen of a predetermined specimen axial length. The stylet includes means co-acting with the cannula for storing multiple, sequentially obtained specimens within the instrument. While multiple samples may be acquired with this device, there is no provision for separating the samples from each other or maintaining the integrity of the individual samples. In addition, the volume of tissue collected per entry into the body cannot exceed the capacity of the receiving notch.
U.S. Pat. No. 4,651,753, entitled "ENDOSCOPIC MULTIPLE BIOPSY INSTRUMENT," issued to Lifton, describes a biopsy instrument for use with an endoscope which includes a rigid cylindrical end attached to the distal end of a flexible arrangement of tubes. The rigid end comprises a cylindrical body having a cavity therein. The cavity extends towards the distal end of the body and is of size sufficient to hold plural samples therein. Inside the cylindrical body is a passageway which serves as a conduit for aspiration of tissue into the cavity and cylindrical body and a knife for cutting the tissue. Furthermore, a plunger is arranged coaxially with the knife for pushing individual biopsy samples into the distal end cavity of the cylindrical body. This device is clearly for endoscopic use and would be inappropriate for use in obtaining samples from a breast or organ interior. Although this device employs an active means to urge tissue into the receiving notch, it bears the same deficiencies as the Chin et al. device--the volume of tissue collected per bodily insertion cannot exceed the collection chamber volume, the origin of the samples cannot be differentiated, and the samples recovered must be manually handled for preparation.
When target tissue lies deep within patient, the need to utilize some form of imaging to direct the distal end of the biopsy system to the desired target further complicates the use of automated tissue sampling devices. Such imaging techniques, as mentioned above, may include fluoroscopic, ultrasound, CT scanning, or MRI equipment. If fluoroscopy is used, the large handle associated with mechanized biopsy guns may obscure visualization of the target and needle tip. When performing a CT guided biopsy procedure, the physician must check the progress of the biopsy instrument intermittently while it is advanced toward the target. Such CT guided procedures generally require the physician to release his or her grip on the biopsy instrument to allow the patient to be transported through the scanner for imaging. However, the bulk of the mechanized biopsy instruments described above do not allow scanning to occur because the patient and the biopsy instrument cannot both fit into the scanning aperture. Moreover, the weight of the handle housing for such devices is sufficient to deflect the outer cannula during scanning; therefore, the image that is obtained may not be an accurate indication of the direction of passage. The metal housing associated with some biopsy guns may degrade the CT scanned image by causing major artifacts, thereby limiting the physician's ability to, see the position of the needle in the patient. Even with respect to the previously mentioned BIOPTY-CUT needle placement method described by Parker et al. for use with the BIOPTY biopsy gun, the authors state that the length of the BIOPTY-CUT needle poses gantry clearance problems during CT scanning, and they further state that the act of attaching the gun to the needle after localization can be awkward. Moreover, as already noted, Parker et al. state that the BIOPTY-CUT needle must be "pinned" to the skin before reattachment to the gun.
Virtually all of the various automated biopsy instruments also tend to be heavy, difficult to manipulate, and incorporate biasing mechanisms which are either complicated in construction or require undue force to operate. Such limitations diminish the physician's control over the instrument and the precision with which biopsies may be performed. These instruments may be subject to inadvertent movement or torque which may, in turn, subject the patient to unnecessary trauma and risk. This is especially true of instruments which permit or require adjustment of the relative positions of any of their elements before the cannula is moved forward to sever the tissue sample. Similarly, the length of time required to perform a biopsy increases as the physician's degree of control of the instrument decreases, further elevating the risk to which the patient may be exposed. Finally, both physician and patient are exposed to the risk of inadvertent advancement of the cannula when the instrument is in its charged condition.
It should be evident from the discussion above that percutaneous biopsy techniques offer significant advantages over open biopsy procedures. It should be equally evident that these advantages have been significantly enhanced by the development of semi-automatic and fully automatic sampling devices, coupled with instrumental imaging guidance. However, the overall utility and efficacy of such techniques remain limited by certain constraining factors. As the discussion above has indicated, a major component of the advantage to be gained from the use of automatic spring-loaded sampling devices is the ability of the surgeon/practitioner to handle such devices with one hand, particularly when used in conjunction with hand-held imaging devices such as ultrasound. Thus, in this regard, it is essential that the design of such instruments must evolve within the physical constraints such use imposes.
Such design, of course, can benefit from the use of plastics and other lightweight materials, but limits remain in this area as well. With light weight there is generally an associated loss of strength. This translates into a form of compromise between the need for lighter and more compact designs with the need to provide sufficient compelling force to the sampling and cutting components of the sampling devices so that tissues with the widest possible range of densities can be sampled. It should be recognized here as well that there are other practical constraints on the amount of force that spring-driven sampling devices can bring to bear on the tissue to be sampled. Accepting that the ideal sampling device needs to be capable of one-handed operation, there is an upper limit to how much force biasing springs can exert and still be capable of being single-handedly cocked to the "ready" position for firing. At present this limit seems to be on the order of 8-10 pounds of force, due to the fact that the cocking force must usually be supplied by the practitioner's thumb while holding the device in a appropriate position as guided by the imaging system. The use of mechanical levering can provide an additional means to exert higher pressures even with one-handed operation, but this approach still faces limits in conjunction with spring-loaded devices. Use of levered triggering means also has the potential to add to the complexity of design, manufacture and use of such devices. Even if the maximum force conveniently exerted through one-hand operation can be extended to the 10-15 pounds of force range, the application of forces much beyond that range would almost certainly require two hands for setting or re-setting the device to the firing position.
The further practical effect of such constraints is that typical spring-loaded core biopsy devices must necessarily be limited to use in sampling soft tissues. Although significant uses remain in soft tissue sampling, there are other potentially beneficial applications not currently amenable to spring-loaded sampling devices. Thus, there is a need for automatic sampling devices that are lightweight and streamlined in design to permit facile one-handed operation; at the same time, there is a further need for devices that possess the mechanical strength necessary to incorporate impelling forces sufficient to enable sampling of tissues or cells characterized by greater density than that associated with the majority of typical soft tissue targets. At the same time such devices need to maintain mechanical simplicity as well, particularly in permitting the rapid re-arming and firing of the device for multiple tissue sampling. An additional factor in the design of such devices is the speed with which the actual sampling means enter and excise the desired sample tissue. It has been recognized that to achieve optimal sampling of target tissues with two-stage (stylet/cannula) designs, the speed of motion of the sampling means as it penetrates and excises target tissue can be critical. Thus, sampling force alone does not achieve optimal sampling. If the cannula/stylet action is too rapid, excision of target tissue is adversely affected. In summary, an ideal device would be simple in construction and operation, capable of the application of forces sufficient to sample a wide range of tissues, amenable to automatic operation, and provide optimal tissue sampling.
The inventors of the instant disclosure have discovered that compressed fluid may be utilized to actuate tissue sampling elements in sampling devices capable of both one-handed operation and impelling forces of sufficient magnitude to permit penetration and sampling of tissues with a wide range of densities. Accordingly, there is disclosed in detail herein an invention incorporating advantages addressing the specific requirements enumerated above. These and other advantages will be apparent through reference to the Detailed Description and Figures presented herein.